A power semiconductor module, in which one or more semiconductor elements (semiconductor chips) are equipped in a case sealed with a sealing material, is known as a semiconductor device. The power semiconductor module is, for example, interpreted so that the power semiconductor element is mounted on an insulating substrate. The insulating substrate is constituted of a metal plate, an insulating resin plate formed on one surface of the metal plate, and a circuit plate in which a predetermined circuit is formed so that a conductive metal foil such as copper foil is formed selectively on the insulating resin plate. The metal plate is, for example, composed of the copper foil having excellent conductivity. Further the insulating resin plate is composed of an insulating resin.
The power semiconductor element is fixed to the circuit plate of the insulating substrate with solder, so that an electrode disposed on one face of the power semiconductor element is connected to the circuit plate electrically. Furthermore, connection can be achieved electrically by using bonding wires or the like among another electrode disposed on the other face of the power semiconductor element, the circuit plate, terminals connecting to the outside, and the like.
The power semiconductor chip is accommodated in a housing. Moreover, the sealing material composed of a thermosetting resin is injected to cover the power semiconductor chip and the bonding wires in the housing. This can protect the semiconductor chip, the bonding wires, the circuit plate, and the like in the housing, insulating one from the others.
The sealing material composed of the thermosetting resin has lower adhesive properties to the circuit plate of the insulating substrate than to the insulating resin plate. Further, the sealing material is different from the circuit plate in thermal expansion coefficient. Therefore, the sealing material is liable to peel off from the interface between the sealing material and the circuit plate of the insulating substrate because heat is generated repeatedly when the power semiconductor chip is operated. If the peeling of the sealing material is enlarged to reach a junction of the bonding wire, this might affect the state where the bonding wire is joined.
In order to improve adhesive properties between the sealing material and the circuit plate of the insulating substrate, there is provided a semiconductor device in which a lot of micro recessed parts are formed to the part except the region where a semiconductor chip is mounted on the front surface of the circuit plate in which the semiconductor chip is adhered (Patent Literature 1).